A series of bombings across Iraq has killed at least 22 people, including three policemen, officials said.

Around 50 people are also believed to have been injured in the violence, which struck the northern ethnically-mixed provinces of Kirkuk and Diyala and south of Baghdad in Babil province.

The attacks targeted government officials, security forces and Shi'ite Muslims in the lead-up to major commemoration ceremonies.

No one has yet claimed responsibility.

Tensions between Shi'ite, Kurdish and Sunni factions in Iraq's power-sharing government have been on the rise this year.

Militants continue to strike almost daily, and carry out at least one big attack a month.

The latest violence followed more than a week of protests against Shi'ite Prime Minister Nuri al Maliki by thousands of people from the country's minority Sunni community.

Seven people from the same Sunni family were killed by a bomb planted near their home in the town of Mussayab, south of Baghdad.

And in the Shi'ite majority city of Hilla, also in the south, a parked car bomb went off near the convoy of the governor of Babil province, missing him but killing two other people, police said.

"We heard the sound of a big explosion and the windows of our office shattered. We immediately lay on the ground," said Mohammed Ahmed, 28, who works at a hospital near the site of the explosion.

"After a few minutes I stood up and went to the windows to see what happened. I saw flames and people lying on the ground."

Although the levels of violence have dropped since 2006 and 2007, about 2,000 people have been killed in Iraq this year following the withdrawal of troops last December, who led an invasion in 2003 to overthrow Saddam Hussein.